Various conventional systems include vibration generation apparatuses, which drive a test body to vibrate by a PWM (pulse-width modulation) drive signal. Some of the vibration generation apparatuses generate PWM drive signals by comparing an input signal level with a threshold level as disclosed in JP-A-2005-524077 (US2003/0200803 A1), for example.
According to the vibration generation apparatus described above, however, an analog waveform is utilized in comparing the input signal level with the threshold level. The analog signal is likely to be susceptible to noise or the like. If a circuit is provided to reduce influence of noise, the apparatus becomes large-sized.